The present invention relates to a polishing composition to be used, for example, in polishing for forming wiring in a semiconductor device.
A high-integration and high-speed ultra large scale integrated circuit (ULSI) is manufactured in accordance with a fine design rule. Recently, in order to suppress an increase in wiring resistance, caused by finer wiring in a semiconductor device, a copper containing metal has been increasingly used as a wiring material.
Since the copper containing metal has the property of being difficult to process by anisotropic etching, wiring made of the copper containing metal is formed by the Chemical Mechanical Polishing (CMP) process in the following manner.
First, a barrier film made of a compound containing tantalum is provided on an insulating film having trenches. Next, a conductive film made of the copper containing metal is provided on the barrier film so as to at least fill up the trenches. Subsequently, in the first polishing process, part of the portion of the conductive film, which is positioned outside the trenches, is removed by CMP. In the second polishing process, another part of the portion of the conductive film, which is positioned outside the trenches, is removed by CMP so that the top surface of the barrier film is exposed. Finally, in the third polishing process, the residue of the portion of the conductive film, which is positioned outside the trenches, and the portion of the barrier film, which is positioned outside the trenches, are removed by CMP so that the top surface of the insulating film is exposed Consequently, the portion of the conductive film, which is positioned in the trenches, is left on the insulating film and will act as the wiring.
Japanese Laid-Open Patent Publication No. 2000-160141 discloses a first conventional polishing composition, which comprises an abrasive, alpha-alanine, hydrogen peroxide, and water. Japanese Laid-Open Patent Publication No. 11-21546 discloses a second conventional polishing composition, which comprises an abrasive, an oxidant, a complexing agent, such as citric acid, and a film forming agent, such as imidazole. Japanese Laid-Open Patent Publication No. 6-313164 discloses a third conventional polishing composition, which comprises an abrasive comprising aqueous colloidal silica and a polishing accelerator comprising a persulfate. Japanese Laid-Open Patent Publication No. 2002-75927 discloses a fourth conventional polishing composition, which comprises an abrasive having a primary particle diameter of 50 to 120 nm, a compound of alpha-alanine or the like for forming a chelate with a copper ion, a film forming agent, such as benzotriazole, hydrogen peroxide, and water. The abrasive acts to mechanically polish an object to be polished. Alpha-alanine and the complexing agent act to promote polishing of an object to be polished which is made of the copper containing metal.
When each of the first to fourth conventional polishing compositions is used in CMP in the above second polishing process, a phenomenon called dishing occurs, where the level of the top surface of the conductive film lowers. This is thought to be attributed to removal of the conductive films to an excessive degree, due to an excessively high ability of each of the first to fourth conventional polishing compositions to polish the copper containing metal. The dishing reduces the cross sectional area of the wiring, thereby causing an increase in wiring resistance. The dishing also impairs the flatness of the surface of a semiconductor device, thereby making it difficult to form multi-filmed wiring in the semiconductor device.